1. Field of the Invention
The present invention relates to a liquid crystal display panel, and in particular, to a liquid crystal display panel comprising a columnar spacer.
2. Description of the Related Art
In recent years, in a field of information apparatuses, particularly computers and a field of video apparatuses, particularly televisions, lightweight, compact, and high-definition liquid crystal display devices have been developed. In general, a liquid crystal display device comprises a liquid crystal display panel having an array substrate, an opposite substrate, and a liquid crystal layer sandwiched between the array substrate and the opposite substrate. Each of the array substrate and the opposite substrate has a display area. For example, plastic beads with a uniform particle size are arranged between the array substrate and the opposite substrate as spacers to hold a gap between the two substrates constant. The array substrate and the opposite substrate are joined together by a sealing member shaped like a rectangular frame and disposed outside the display area of each of the substrates.
In a color display active matrix driving liquid crystal display device, a plurality of signal lines and a plurality of scanning lines are disposed on the array substrate in the display area thereof in a matrix. A thin film transistor (hereinafter referred to as TFT) including a semiconductor layer made of, for example, amorphous silicon (a-Si) or polysilicon (p-Si) is disposed in the vicinity of a crossing portion between each of the signal lines and each of the scanning lines. TFTs are connected to respective pixel electrodes formed on the substrate. An alignment film is deposited on the substrate and the pixel electrodes.
In the opposite substrate, a color filter, a common electrode, and an alignment film are sequentially formed on a substrate. The color filter is composed of colored layers colored in red, green, and blue, respectively. The liquid crystal layer is sandwiched between the array substrate and the opposite substrate to form the liquid crystal display device.
Furthermore, a technique for uniformizing the gap between the array substrate and the opposite substrate is disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2006-18238. Jpn. Pat. Appln. KOKAI Publication No. 2006-18238 discloses a technique of forming a columnar spacer on at least one of the array substrate and the opposite substrate by patterning using a photolithography method or the like.
The columnar spacer overlaps the common electrode. Also on the array substrate, the columnar spacer may overlap the pixel electrode. In general, the pixel electrode and the common electrode are formed of ITO (Indium Tin Oxide), which is an inorganic material. In this case, the pixel electrode and the common electrode are fragile like glass. Thus, when the columnar spacer overlaps the pixel electrode and the common electrode, then upon being subjected to impact, the liquid crystal display panel cannot sufficiently absorb the impact. As a result, the common electrode or the like may be damaged. Furthermore, at low temperatures, the liquid crystal display panel cannot sufficiently follow a variation in volume, resulting in a high likelihood of generating bubbles. This degrades display quality.